Back to the full dot-point answer
VICChemistryQuick questions
Unit 3: How can design and innovation help to optimise chemical processes?
Quick questions on Galvanic cells, fuel cells and cell EMF: VCE Chemistry Unit 3
15short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is what a galvanic cell does?Show answer
A galvanic cell (also called a voltaic cell) converts the chemical energy of a spontaneous redox reaction into electrical energy. The two half-reactions are physically separated into half-cells so that the electrons released by the oxidation half-cell are forced to travel through an external circuit to reach the reduction half-cell. That moving charge is the electric current the cell delivers.
What is components?Show answer
A galvanic cell has five components:
What is direction of charge?Show answer
The ion flow keeps each half-cell electrically neutral. As the anode half-cell builds up Zn^2+, anions move in to balance the charge; as the cathode half-cell consumes Ag^+, cations move in to replace the lost positive charge.
What is calculating cell EMF?Show answer
The EMF (or cell potential) E°_cell is the voltage the cell delivers under standard conditions (1 mol L^-1 solutions, 25°C, 1 atm for gases).
What is primary, secondary and fuel cells?Show answer
The three cell types in the VCE Study Design:
What is the hydrogen oxygen fuel cell?Show answer
A widely examined example. In an acidic electrolyte:
What is primary cells?Show answer
The redox reaction is one way. Once the reactants are consumed, the cell is dead and discarded. Cheap, simple, used in low-drain applications (remote controls).
What is secondary cells?Show answer
The redox reaction is reversible. Applying an external voltage in reverse drives the reaction backwards, regenerating the original reactants. Higher initial cost, but cheaper per use over the cell's life.
What is fuel cells?Show answer
A continuous supply of fuel (e.g. H2) and oxidant (O2) enters the cell. The cell runs as long as the supply continues.
What is calling the anode positive?Show answer
In a galvanic cell, the anode is negative and the cathode is positive. (In an electrolytic cell the polarity is reversed; this is a common point of confusion.)
What is multiplying E° by coefficients?Show answer
E° is a per-electron property. Multiplying or dividing the half-equation does not change E°.
What is forgetting to subtract a negative E°?Show answer
E°_cell = E°(cathode) - E°(anode). If the anode E° is negative, subtracting a negative gives a larger positive E°_cell. Sign errors here cost marks.
What is reversing the salt bridge ion direction?Show answer
Cations chase the cathode (cation goes to cathode). Anions stay with the anode (anion to anode).
What is calling a fuel cell "rechargeable"?Show answer
A fuel cell is not recharged; it runs continuously while fuel is supplied. Secondary cells are recharged.
What is drawing a cell with no salt bridge?Show answer
Without the salt bridge the cell stops within seconds because charge cannot be balanced.